(cont. 4 of 4)
We have already noted with Fischcoff that "hindsight is not foresight". A way forward is to make observations and derive general principles that can be used to guide design; generalising as much as possible but not more.
Reducing risk of error at the sharp end: Design for error, design for users.
Areas of considering the human operator (these will be discussed more next week).
Anthropometrics and biomechanics: can it be used with ease.
Behavioural issues: can the task be done with ease, how is it used.
Cognitive issues: does the operator know what to do, can the operator do it.
Rolfe, who gave the example above, states: (a) humans have limited information processing capacities, (b) human behaviour is influenced by past experiences, and (c) human performance is affected by adverse physical, psychological and physiological influences. We will talk more about this in the next part of the course.
Note also that the issues I raise from Norman deal mostly with cognitive issues, although when considering, for example, door handles in schools under the consideration of 'forcing functions', Norman is considering anthropometrics.
Social issues: can people communicate effectively. Are there problems with the way in which the tasks are divided up? Is the social milieu conducive to working the the way the operator is required to work?
Don Norman's book The psychology of everyday things offers a number of (rather less gruesome) illustrations of poorly designed things. It also discusses the way in which design can be changed to ensure better designs. These will be discussed later in the course.
To consider some everyday examples:-
"If I were placed in the cockpit of a modern day jet airliner, my inability to perform gracefully and smoothly would neither surprise nor bother me. But I shouldn't have trouble with doors and switches, taps and cookers".
A friend of mine told me of the time he got trapped in the doorway of a post office in a European city. The entrance was an imposing row of perhaps six glass swinging doors, followed immediately by a second, identical row. That's a standard design; it helps reduce the airflow and maintain the indoor temperature of the building.
My friend pushed on the side on one of the leftmost pair of outer doors. It swung inward and he entered the building. Then, before he could get to the next row of doors he was distracted and turned around for an instant. He didn't realise it at the time, but he had moved slightly to the right. So , when he came to the next door and pushed it nothing happened. "Hmmmm" he thought, "must be locked". So he pushed the side of the adjacent door. Nothing. Puzzled, my friend decided to go outside again. He turned around and pushed the door. Nothing. He tried the adjacent door. Nothing. The door he had just come in through no longer worked. He turned around once more and tried the inside doors again. Nothing. Concern turned told panic. He was trapped! Just then, a group of people on the other side of the entrance way (far to the right) passed easily through both sets of doors. My friend hurried over and followed them through.
How could such a thing happen? A swinging door has two sides. One is pillar and hinge, the other moves. To open the door one must push the movable sides. Pushing on the hinges has no effect. In this case, the designer had aimed for beauty not utility. No distracting lines, no visible pillars, no visible hinges. So how can you tell which side to push? (Norman, 1989, p. 2).
There is a very easy principle that Norman derives from this story -- and others; namely the critical importance of visibility in design. Good design involves making crucial information visible.
Think of a slide projector on which the slides are changed with a single button. Sometimes one wants to move forwards and sometime backwards. To go forwards requires a short button press and to go backward a long button press. This is invisible and makes for very difficult use, even when one knows how to do it. Getting the timing right may be difficult, and this function is not likely to be apparent to all new users.
However, visibility is to my mind not an adequate guideline. As Norman says, too much visibility is a bad thing. Norman offers the example of a washer / drier that had multiple controls and symbols. There was no way to discern which controls did which thing without looking at the instructions. Think of a photocopier. Too much information is very confusing because it is hard to know what is salient for the task at hand.
What we can learn from considering principle of visibility is that we cannot take a simple rule like "visibility" and apply it. Visibility has to be interpreted for the specific context in which that user will be performing their tasks. As a principle, "visibility" need to be expressed as
"visibility of the appropriate information for achieving relevant tasks"
There are a number of examples in Norman's book. One of the most interesting is a fridge freezer and the model of how it works. Although a simple device it turns out to have a complex usability analysis.
FEEDBACK
CONSISTENCY
UNDERSTANDING: e.g. having an adequate mental model.
From this we can also see that ergonomics is not simply about designing to fit the user -- it is also critically about designing to fit the user's tasks. Fitting the environment to the person must be more broadly interpreted as fitting the environment to the tasks, goals and expectations of the person.
Finally, remember the main concepts I raised last week and earlier today: that when designing we design with functionality in mind, but also with usability and learnability. The conditions under which the device is used needs to be considered: think about the tasks the user is performing. For example, the pilots at Kegworth had never flown that plane in an emergency situation.
Another example: the dials at Three Mile Island. Think about your user and their tasks: anthropometrics, biomechanics, behavioural and task issues, cognitive issues (including level of expertise, i.e. how much knowledge they have, the feedback you give them, the visibility of the items they need to use -- clutter) and social issues. We will think about these issues in more detail next week.
These are three ways of considering designs. Together they make for "usefulness". From Norman's examples we can see that functionality and aesthetics drive a lot of designs. This in turn is driven often by saleability. More and more usability issues are coming to the fore, and in the last 10 years "user-friendly" has become a term we hear more often. As people refuse to buy badly designed articles, this can only get better.
'Functionality' is what the device/object does. This is what can be achieved with it. So, the functionality of a stapler is to staple (you could of course have unplanned functions like stapler as paper-weight). The functionality of computer equipment usually means what you can do with it. The functionality of a washing machine is to wash all the clothes for which it has program specifications, and then to spin them. The functionality of a washer-drier extends this to provide drying functions as well.
The 'Usability' of a device/artifact is how easy it is to use. This depends on how well it has been designed for the target user group and with the target tasks in mind as well as how well supported it is. Thus I would say that some computer systems are more "usable" than others. Offer an example of a graph and extracting information
The "Learnability" of a device is how easy it is to learn how to use it.
`Functionality' + `Usability' + "Learnability" = "usefulness"